From German patent application No. 1,964,469 an atomic absorption spectrometer is known wherein the radiation originates from a single light source designed as a line emitter, the radiation of which passing through the sample is frequency modulated by use of the longitudinal Zeeman effect. In this prior atomic absorption spectrometer a hollow cathode lamp is arranged between the pole pieces of a solenoid. One of the pole pieces has a bore through which the measuring light beam passes. Then the measuring light beam is directed through a flame serving as atomizing device and a monochromator and impinges upon a photo-electrical detector. The solenoid is arranged to be switched on and off, whereby the atomic absorption of the sample atoms compensated with respect to the background absorption can be determined from the difference of the signals with the solenoid switched off and switched on.
In this prior art atomic absorption spectrometer the emission lines of the line emitting light source are periodically shifted by the Zeeman effect and thus the emitted light frequency is modulated and not the absorption lines of the sample. This may cause problems when a hollow cathode lamp is used as light source because the discharge of the hollow cathode lamp is influenced by the magnetic field, as already mentioned in German Patent Application No. 1,964,469.
From German patent application No. 2,165,106 it is known to apply the magnetic field of a solenoid arranged to be switched on and off to the atomizing device, i.e. to the sample which is to be atomized, instead to the light source. Therein the atomizing device is a flame. The magnetic field is applied perpendicular to the direction of propagation of the measuring light beam. A splitting of the absorption lines due to the "transverse" Zeeman effect is effected, which again effects a relative shift of the emission lines of the measuring light beam and the absorption lines of the sample. Again it can be discriminated between atomic absorption by the atoms of the element looked for and non-specific background absorption by switching the magnetic field on and off.
From German patent application No. 2,165,106 an atomic absorption spectrometer is known in which a sample cavity is formed by a housing which sample cavity is passed through by a measuring light beam. An atomizing device is arranged in the sample cavity. A measuring vessel in which hydrides are decomposed which were formed from a sample by chemical reactions, a burner or a furnace for electrothermal atomization (graphite tube vessel) can be optionally provided as atomizing device.
With respect to the prior art German patent application No. 29 50 105 describes a construction in which depending on the kind of atomization the suitable atomizing device is individually built into the sample cavity and is adjusted in the sample cavity. After building in and after adjustment the connections for the supply of current, inert gas and cooling liquid or for fuel gas and oxidant agent have to be installed.
Compared thereto German patent application No. 29 50 105 describes an atomic absorption spectrometer in which at least two of the above mentioned atomizing devices, hydride measuring vessel, burner or furnace are composed to a componentry which is fixedly installed in the sample cavity. The measuring light beam can be optionally passed through a respective atomization device being in operation.
German patent application No. 29 50 105 relates only to the installation of the atomizing device in a narrow sense that means the burner or the furnace. Each mode of operation however requires additional apparatus. A burner requires control devices for controlling or regulating the fuel gas or oxydant agent supplies. A power unit which supplies the high and adjustable currents required belongs to a furnace for the electrothermal atomization. These additional apparatus are generally designed as separate components which are arranged beside the atomic absorption spectrometer and generally are quite clumsy. The atomic absorption spectrometer according to German patent application No. 29,50,105 allows no compensation of the background absorption in that the atomic absorption of the atoms of the sample is "eliminated" by the Zeeman effect by means of a magnetic field applied.
In the atomic absorption spectrometer of German patent application No. 29 50 105 discussed before all atomizing devices which can be optionally used are permanently installed in the apparatus. Also the signal processing has to be provided for the different modes of atomization. Thereby the atomic absorption spectrometer becomes clumsy and expensive.
From German patent application No. 35 28 300 an atomic absorption spectrometer with a burner is known in which the burner is adjustably arranged on a carriage. The carriage is movable between a first and a second position by a servomotor. In a first position the cloud of atoms is generated by the burner in the area of the measuring light beam extending stationary. In the second position the burner with its flame is arranged outside the measuring light beam extending stationary, such that a measurement is made which is not influenced by the atomized sample. Here the compensation of the drift of the zero line is the subject matter.
A further atomic absorption spectrometer is known in which compensation of the background absorption is permitted by periodically generating a strong magnetic field at the location of the sample in a furnace for electrothermal atomization, whereby the absorption lines of the sample are shifted relative to the lines of the measuring light beam by the Zeeman effect. In this prior atomic absorption spectrometer an atomic absorption spectrometer arranged for operating without "Zeeman effect" is used as basic instrument. A "Zeeman auxiliary apparatus" is attached to this basic apparatus, this auxiliary apparatus comprising a furnace in an additional sample cavity and a solenoid for generating the Zeeman effect.